Plastic in any form is a nuisance to the well-being of the environment. The ‘pestilence’ caused by it is mainly due to its non-degradable nature. With the industrial boom and the population explosion, the usage of plastic products has increased. A steady increase has been observed in the use of plastic products, and this has accelerated the pollution. Several attempts have been made to curb the problem at large by resorting to both chemical and biological methods. Chemical methods have only resulted in furthering the pollution by releasing toxic gases into the atmosphere; whereas; biological methods have been found to be eco-friendly however they are not cost effective. This paves the way for the current study where fungal isolates have been used to degrade polyethylene sheets (HDPE, LDPE). Two potential fungal strains, namely, Penicillium oxalicum NS4 (KU559906) and Penicillium chrysogenum NS10 (KU559907) had been isolated and identified to have plastic degrading abilities. Further, the growth medium for the strains was optimized with the help of RSM. The plastic sheets were subjected to treatment with microbial culture for 90 days. The extent of degradation was analyzed by, FE-SEM, AFM and FTIR. Morphological changes in the plastic sheet were determined.

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We study a specific type of lifetime broadening resulting in the well-known exponential "Urbach tail" density of states within the energy gap of an insulator. After establishing the frequency and temperature dependence of the Urbach edge in GaAs quantum wells, we show that the broadening due to the zero-point optical phonons is the fundamental limit to the Urbach slope in high-quality samples. In rough analogy with Welton's heuristic interpretation of the Lamb shift, the zero-temperature contribution to the Urbach slope can be thought of as arising from the electric field of the zero-point longitudinal-optical phonons. The value of this electric field is experimentally measured to be 3  kV cm-1, in excellent agreement with the theoretical estimate.

High pressure behaviour of nanocrystalline YCrO is investigated up to 10 GPa using electrical, magnetic, synchrotron x-ray diffraction and Raman spectroscopy measurements. High pressure dielectric constant measurements show a sharp peak at 4.5 GPa, though the sample is found to be in ferroelectric phase up to the highest pressure of our study from piezoelectric current measurements. X-ray diffraction measurements show absence of any structural phase transition, however anomalies are observed in the unit cell structural parameters at about 4.3 GPa and the Y-atom position shows a maximum shift at the same pressure. In the absence of any structural transition, anomalous behaviour of relevant Raman modes with minimum in the Raman band width at about same pressure indicate towards a spin-phonon interaction. AC magnetic measurements in the toroid anvil cell show an anomalous enhancement of magnetic moment above 4 GPa indicating a collective magnetic response of nanoparticles.

In a "thought experiment," now a classic in physics pedagogy, Feynman visualizes Young's double-slit interference experiment with electrons in magnetic field. He shows that the addition of an Aharonov-Bohm phase is equivalent to shifting the zero-field wave interference pattern by an angle expected from the Lorentz force calculation for classical particles. We have performed this experiment with one slit, instead of two, where ballistic electrons within two-dimensional electron gas diffract through a small orifice formed by a quantum point contact (QPC). As the QPC width is comparable to the electron wavelength, the observed intensity profile is further modulated by the transverse waveguide modes present at the injector QPC. Our experiments open the way to realizing diffraction-based ideas in mesoscopic physics.

Ammonia-molecular-beam epitaxial growth and optical properties of GaN/AlGaN quantum wells J. Appl. Phys. 91, 9685 (2002); 10.1063/1.1479756Localized quantum well excitons in InGaN single-quantum-well amber light-emitting diodesThe GaP/AlP/GaP heterostructure has an indirect gap both in real as well as momentum space, making the first order radiative recombination doubly forbidden. Nevertheless, we have observed relatively efficient emission from these structures. This paper comprehensively studies the origin of this improved light emission through a detailed analysis of the photoluminescence (PL) spectra. Our observations suggest that localized excitons within the acceptor states in GaP close to the heterostructure interface are enough for efficient light emission in these structures, doing away with the need for more complicated structures (superlattices or neighboring confinement structures). This real space localization of holes, close to the interface, apart from increasing the wave function overlap, also relaxes the delta-function momentum selection rule. Independent experimental evidence for this assertion comes from (i) the PL spectrum at high excitation power where transitions from both the localized as well as extended states are independently observed, (ii) the observation that extended states emission has the expected band-bending-induced blue-shift with increase in excitation power, whereas the localized states do not, (iii) observation of phonon replicas for PL from localized states, and (iv) observation of persistent photoconductivity at low temperature. Finally, we propose a simple analytical model that accounts for both the type-II nature as well as the indirect bandgap to explain the improvement of radiative recombination efficiency with increased localization. The experimental observations are reproduced within an order of magnitude. The model is very general and it also provides a framework to study the optical properties of other such (type-II and/or indirect gap) heterostructures. V C 2013 AIP Publishing LLC. [http://dx.